DefaultReactiveElasticsearchClient handle 5xx error with empty body

Original Pull Request spring-projects#1713 
Closes spring-projects#1712

Author: sothawo

Diff for: src/main/java/org/springframework/data/elasticsearch/client/reactive/DefaultReactiveElasticsearchClient.java

@@ -866,6 +866,10 @@ private <T> Publisher<? extends T> handleServerError(Request request, ClientResp
 		String mediaType = response.headers().contentType().map(MediaType::toString).orElse(XContentType.JSON.mediaType());
 
 		return response.body(BodyExtractors.toMono(byte[].class)) //
+				.switchIfEmpty(Mono
+						.error(new ElasticsearchStatusException(String.format("%s request to %s returned error code %s and no body.",
+								request.getMethod(), request.getEndpoint(), statusCode), status))
+				)
 				.map(bytes -> new String(bytes, StandardCharsets.UTF_8)) //
 				.flatMap(content -> contentOrError(content, mediaType, status))
 				.flatMap(unused -> Mono

Diff for: src/test/java/org/springframework/data/elasticsearch/client/reactive/DefaultReactiveElasticsearchClientTest.java

@@ -22,20 +22,29 @@
 import reactor.core.publisher.Mono;
 import reactor.test.StepVerifier;
 
+import java.net.URI;
+import java.util.Optional;
 import java.util.function.Function;
 
+import org.elasticsearch.ElasticsearchStatusException;
+import org.elasticsearch.action.get.GetRequest;
 import org.elasticsearch.action.search.SearchRequest;
 import org.elasticsearch.client.Request;
 import org.elasticsearch.index.query.QueryBuilders;
 import org.elasticsearch.search.builder.SearchSourceBuilder;
 import org.elasticsearch.search.fetch.subphase.FetchSourceContext;
-import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.mockito.ArgumentCaptor;
 import org.mockito.Mock;
+import org.mockito.Spy;
 import org.mockito.junit.jupiter.MockitoExtension;
+import org.springframework.http.HttpStatus;
+import org.springframework.web.reactive.function.client.ClientResponse;
+import org.springframework.web.reactive.function.client.WebClient;
 import org.springframework.web.reactive.function.client.WebClient.ResponseSpec;
+import org.springframework.web.util.UriBuilder;
 
 /**
  * @author Peter-Josef Meisch
@@ -46,30 +55,24 @@ class DefaultReactiveElasticsearchClientTest {
 	@Mock private HostProvider hostProvider;
 
 	@Mock private Function<SearchRequest, Request> searchRequestConverter;
+	@Spy private RequestCreator requestCreator;
 
-	private DefaultReactiveElasticsearchClient client;
-
-	@BeforeEach
-	void setUp() {
-		client = new DefaultReactiveElasticsearchClient(hostProvider, new RequestCreator() {
-			@Override
-			public Function<SearchRequest, Request> search() {
-				return searchRequestConverter;
-			}
-		}) {
-			@Override
-			public Mono<ResponseSpec> execute(ReactiveElasticsearchClientCallback callback) {
-				return Mono.empty();
-			}
-		};
-	}
+	@Mock private WebClient webClient;
 
 	@Test
 	void shouldSetAppropriateRequestParametersOnCount() {
 
+		when(requestCreator.search()).thenReturn(searchRequestConverter);
 		SearchRequest searchRequest = new SearchRequest("someindex") //
 				.source(new SearchSourceBuilder().query(QueryBuilders.matchAllQuery()));
 
+		ReactiveElasticsearchClient client = new DefaultReactiveElasticsearchClient(hostProvider, requestCreator) {
+			@Override
+			public Mono<ResponseSpec> execute(ReactiveElasticsearchClientCallback callback) {
+				return Mono.empty();
+			}
+		};
+
 		client.count(searchRequest).as(StepVerifier::create).verifyComplete();
 
 		ArgumentCaptor<SearchRequest> captor = ArgumentCaptor.forClass(SearchRequest.class);
@@ -79,4 +82,33 @@ void shouldSetAppropriateRequestParametersOnCount() {
 		assertThat(source.trackTotalHitsUpTo()).isEqualTo(TRACK_TOTAL_HITS_ACCURATE);
 		assertThat(source.fetchSource()).isEqualTo(FetchSourceContext.DO_NOT_FETCH_SOURCE);
 	}
+
+	@Test // #1712
+	@DisplayName("should throw ElasticsearchStatusException on server 5xx with empty body")
+	void shouldThrowElasticsearchStatusExceptionOnServer5xxWithEmptyBody() {
+
+		when(hostProvider.getActive(any())).thenReturn(Mono.just(webClient));
+		WebClient.RequestBodyUriSpec requestBodyUriSpec = mock(WebClient.RequestBodyUriSpec.class);
+		when(requestBodyUriSpec.uri((Function<UriBuilder, URI>) any())).thenReturn(requestBodyUriSpec);
+		when(requestBodyUriSpec.attribute(any(), any())).thenReturn(requestBodyUriSpec);
+		when(requestBodyUriSpec.headers(any())).thenReturn(requestBodyUriSpec);
+		when(webClient.method(any())).thenReturn(requestBodyUriSpec);
+		when(requestBodyUriSpec.exchangeToMono(any())).thenAnswer(invocationOnMock -> {
+			Function<ClientResponse, ? extends Mono<?>> responseHandler = invocationOnMock.getArgument(0);
+			ClientResponse clientResponse = mock(ClientResponse.class);
+			when(clientResponse.statusCode()).thenReturn(HttpStatus.SERVICE_UNAVAILABLE);
+			ClientResponse.Headers headers = mock(ClientResponse.Headers.class);
+			when(headers.contentType()).thenReturn(Optional.empty());
+			when(clientResponse.headers()).thenReturn(headers);
+			when(clientResponse.body(any())).thenReturn(Mono.empty());
+			return responseHandler.apply(clientResponse);
+		});
+
+		ReactiveElasticsearchClient client = new DefaultReactiveElasticsearchClient(hostProvider, requestCreator);
+
+		client.get(new GetRequest("42")) //
+				.as(StepVerifier::create) //
+				.expectError(ElasticsearchStatusException.class) //
+				.verify(); //
+	}
 }